The present invention relates to the cooling of dynamoelectric machines such as large turbine generators, and more particularly to the means for supplying coolant liquid to the windings of liquid-cooled rotors for such machines.
Large turbine generators are usually of the inner cooled, or direct cooled, construction in which a coolant fluid is circulated through duct means in the stator and rotor slots in direct thermal relation with the current-carrying conductors inside the ground insulation. This type of construction provides a very effective cooling system which has made it possible to attain very high ratings for large generators. The coolant fluid used in these machines heretofore has usually been hydrogen which fills the gas-tight housing and is circulated through the ducts of the stator and rotor windings and through radial or axial ducts in the stator core. As further increases in the maximum capacities of these large generators have become necessary, further improvements in cooling have been required and have been obtained by the use of more efficient coolant fluids such as liquids. A very considerable improvement in cooling has been obtained in this way by circulating a liquid coolant such as water through the ducts of the stator winding, and a substantial further improvement can be obtained by similarly circulating a coolant liquid through passages in the rotor winding.
Coolant liquid such as water is preferably supplied to the rotor of a large generator, and discharged therefrom, through the shaft bore so that the sealing problem can be minimized by introducing and discharging the liquid at locations of minimum radius where the centrifugal force on the liquid is at a minimum. When the liquid is thus introduced through the shaft, it flows from the bore through radial passages to an annular distribution chamber on the surface of the rotor from which it can be distributed to the conductors of the rotor winding through suitable tubes or hydraulic connectors. After flowing through the rotor conductors, the heated coolant may flow through similar tubes and passages at the opposite end of the rotor and be discharged through a central bore at that end, or it may return to the same end at which it entered to be discharged. Arrangements of this general type are shown, for example, in the U.S. Pat. Nos. to Curtis et al, 3,733,502 and Gibbs et al, 3,131,321, and in a copending application of F.P. Fidei et al (Case WE-43,520), Ser. No. 444,582, filed Feb. 21, 1974 and assigned to the Assignee of the present invention.
In this type of construction, the tubes through which the coolant flows to and from the winding are preferably placed in longitudinal slots in the rotor shaft and connected to the winding conductors in the end turn portions of the winding. The annular distribution chamber extends completely around the shaft and insulating hoses or connectors are provided for flow of liquid from the chamber and return thereto. The insulating hoses correspond in number to the number of coolant tubes and are distributed around the circumference of the annular chamber. The individual coolant tubes are connected to these insulating hoses and extend from the hoses into the axial slots, the necessary number of tubes being placed in each slot for connection to the individual winding conductors. The tubes must thus be brought inward from the radius of the distribution chamber to the radius of the slots, and brought together into groups of the appropriate numbers of tubes. The tubes therefore pass through a transition region in which they are formed in a manner to bring them into the necessary groups, and they must be adequately supported in this region against the high rotational forces to which they are subjected during operation and in a manner to prevent significant cycling stresses which could result in fatigue. The arrangement should also be such that the tubes can be manufactured and assembled on the rotor without unusual difficulty and at a reasonable cost, and so that possible removal and replacement of tubes or groups of tubes for repair purposes is facilitated to minimize the time and cost involved. It is also desirable to minimize the space required for this transition region in order to avoid any undue increase in the length of the rotor.